Conventional wireless systems have difficulty operating in complicated, cluttered, environments. This is because their high frequency links suffer from “multipath.” Multipath is multiple propagation of signals along many paths. Multipath tends to scramble data communications and confound location systems. Multipath limits the utility of wireless systems in dangerous environments where robust data links and reliable location information are most essential.
Workers in potentially hazardous environments like nuclear and chemical plants, coal mines, industrial facilities, or in emergency response or military operations might require real time location awareness. Any number of industrial accidents have been made far worse because rescuers were unable to locate injured workers, delaying rescue and risking the rescuers' own safety by prolonged searching. A reliable data link could enable low data rate communication of workers' vital signs or environmental sensor data.
By operating at low frequencies with long wavelengths, near-field wireless systems avoid the problem of multipath. A wireless link operating within a typical maximum range of around one-half wavelength. Near-field wireless systems have demonstrated a remarkable ability to provide accurate location data even in complicated industrial environments.
As accurate as near-field wireless systems are, there is always need for additional accuracy.
There is a further need for a wireless system that can provide robust voice and data communications in complicated wireless propagation environments.
There are many applications for range and position information. Tracking assets, people, animals and objects generally. Commercial businesses have a need to track customers, employees, merchandise equipment. Warehouse operations need to track merchandise, equipment, and employees. Theme parks need to track customers, equipment, and employees. The military, during training exercises, needs to track soldiers, equipment. Each of these applications often involves indoor or urban canyon environments were GPS is unavailable or operates poorly or has insufficient accuracy to pinpoint an object location to a particular room, shelf or bin. These tracked objects often have a need for data transmission, such as a temperature or shock sensor or other device associated with the device or for other data transmission.
Near field systems appear to offer good resistance to multipath and may be operated indoors independent of GPS. Near field systems are challenged by FCC power restrictions and an ever increasing need for greater accuracy and range as more potential applications are envisioned for the systems.
In view of the foregoing, there is a need for electromagnetic ranging systems capable of tracking people, assets, and objects generally in complex multipath environments, such as indoor environments, industrial and warehouse environments, and other environments where GPS and related techniques are unusable. There is a further need to convey modulated data in association with the ranging system without adding substantial complexity and cost to the system.